(^) Lighter PIT technology with 3.5 cm diameter tubes (Fig. 13.23b) was used by the
VERTEX studies in the 1980s led by John Martin. The main trap contents were
primarily amorphous mats of organic goo, marine “snow”. All sorts of organic
particles get stuck in the bits and sheets of snow. Live phytoplankton (microflagellates
predominate in numbers, large cells in the flux) are transported to great depths;
radiolarians and other protists are common; fecal pellets are present of animals from
protozoa (minipellets) to crabs and salps, and all of these are bound in an amorphous
mucoid background (e.g. Silver & Gowing 1991). Bacteria are also numerous. In data
presented by Urrere and Knauer (1981), pellet fluxes from copepods and other
plankton were of the order of 200,000–325,000 m−2 d−1 in the upper 100 m. That
seems a huge number of pellets. However, it is not surprising, given the number of
copepods in the upper water column and their rate of defecation. Below 100 m, the
numbers progressively fell to 35,000 m−2 d−1, then increased again, probably due to
mid-water consumption and “repackaging” of particles. It is the repeated digestion of
the sinking matter that accounts for the reduction downward of organic mass flux.
Despite the large number of pellets, they contributed only about 10% of carbon flux in
upper levels and 3% below 1500 m. Snow is the main transport mechanism. All the
trappers seem to agree on that.
(^) As a further example, we show the quantification by Berelson (1997), using large
conical traps of the fraction of surface production reaching the seafloor along a
transect across the equator at 140°W (Fig. 13.26). Primary production was estimated
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